Recent developments in the analysis of the cardiac signal in real time under the influence of autonomic control, have led to the development of a new painful stress quantification index. A monitor has recently been developed and provides an index of nociception and analgesia (ANI index). It is based on the study of the variability of the heart rate control changes in sympathetic and parasympathetic systems in response to stimuli. Clinical correlations have been completed for most of adult patients during or after general anesthesia. The validation of this nociception index has not been validated for pediatric care in a sector where particular attention is given to control pain.